EP2560279A1 - Wireless apparatus and distortion compensation method used on time division duplex system - Google Patents
Wireless apparatus and distortion compensation method used on time division duplex system Download PDFInfo
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- EP2560279A1 EP2560279A1 EP12188058A EP12188058A EP2560279A1 EP 2560279 A1 EP2560279 A1 EP 2560279A1 EP 12188058 A EP12188058 A EP 12188058A EP 12188058 A EP12188058 A EP 12188058A EP 2560279 A1 EP2560279 A1 EP 2560279A1
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- signal
- distortion compensation
- reception
- transmission
- feedback
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/32—Modifications of amplifiers to reduce non-linear distortion
- H03F1/3241—Modifications of amplifiers to reduce non-linear distortion using predistortion circuits
- H03F1/3247—Modifications of amplifiers to reduce non-linear distortion using predistortion circuits using feedback acting on predistortion circuits
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/20—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers
- H03F3/24—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers of transmitter output stages
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/02—Transmitters
- H04B1/04—Circuits
- H04B1/0475—Circuits with means for limiting noise, interference or distortion
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F2201/00—Indexing scheme relating to details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements covered by H03F1/00
- H03F2201/32—Indexing scheme relating to modifications of amplifiers to reduce non-linear distortion
- H03F2201/3233—Adaptive predistortion using lookup table, e.g. memory, RAM, ROM, LUT, to generate the predistortion
Definitions
- the embodiments discussed herein are related to a wireless apparatus and a distortion compensation method used on a time division duplex system.
- a transmission amplifier For wireless communication apparatuses using a multi-phase shift keying modulation system for a high efficiency transmission, significant design conditions for reducing power leakage to adjacent channels by reducing nonlinear distortion of a power amplifier in a transmission unit (hereinafter, described as a "transmission amplifier” in some cases) are provided.
- a transmission amplifier For example, in a case in which a channel uses a frequency at a boundary of a frequency band assigned to a carrier, noise occurs to adjacent channels for other carriers because of power leakage from the channel in a wireless communication.
- Distortion compensation amplifiers that compensate for nonlinear distortion employ a pre-distortion technique in some cases.
- a transmission signal is corrected in advance using data having characteristics inverse to characteristics of nonlinear distortion (hereinafter, described as “distortion compensation data" in some cases).
- the corrected signal is used as a signal to be input to a transmission amplifier.
- one portion of the transmission signal amplified by the transmission amplifier is fed back.
- the transmission signal is compared with the transmission signal prior to being corrected using the distortion compensation data, and the distortion compensation data are updated.
- a loop system including the transmission amplifier and a feedback system that are used to update the distortion compensation data is described as a "distortion compensation loop" in some cases.
- a signal that is fed back in the distortion compensation loop (hereinafter, described as a "feedback signal” in some cases) is required that the signal has characteristics of an output signal of the transmission amplifier.
- the transmission signal is reflected by an antenna because of fluctuation in load imposed on the antenna that is caused by deterioration of conditions for placing the antenna or the like. Then, in some cases, the reflected transmission signal (hereinafter, described as a "return signal” in some cases) leaks into the distortion compensation loop. Accordingly, the feedback signal is not considered as a signal that is obtained in consideration of the output signal of the transmission amplifier.
- a technique for solving the above-mentioned problem a technique is disclosed, in which a vector adjustment circuit capable of performing phase adjustment or amplitude adjustment is provided, and in which cancellation of a return signal that has leaked into a feedback signal is performed (see International Publication Pamphlet No. WO2006/059372 ).
- TDD system time division duplex system
- Fig. 1 is a diagram for explaining a TDD system.
- a base station (BS) and mobile stations (MS) 1 to 3 exist in the same cell.
- the base station (BS) and the mobile stations (MS) 1 to 3 alternately perform transmission and reception of signals therebetween at different timings in TDD frames using the same frequency.
- Fig. 1 illustrates a four-channel multiplexing multicarrier system.
- Each of the TDD frames is divided into a transmission time period, in which communication in a downward direction from the base station (BS) to a mobile station (MS) is performed, and a reception time period, in which communication in an upward direction from a mobile station (MS) to the base station (BS).
- Four time slots are assigned to each of the transmission time period and the reception time period.
- time slots T1 to T4 are assigned to the transmission time period
- time slots R1 to R4 are assigned to the reception time period.
- the time slots T1 and R1 are control channels, and are used to perform transmission/reception of a control signal between the base station (BS) and each of the mobile stations (MS) in a corresponding one of the TDD frames.
- the base station (BS) and the mobile station 1 (MS1) perform transmission/reception of a control signal therebetween.
- the base station (BS) and the mobile station 2 (MS2) perform transmission/reception of a control signal therebetween.
- the base station (BS) and the mobile station 3 (MS3) perform transmission/reception of a control signal therebetween.
- the time slots T2 to T4 and R2 to R4 are communication channels.
- the base station (BS) and each of the mobile stations (MS) perform transmission/reception of communication signals therebetween in a corresponding one of the TDD frames.
- Figs. 2A to 2B are diagrams illustrating frequency spectra of a transmission signal for explaining influence of nonlinear distortion, and illustrate a case in which the transmission signal is transmitted as one carrier wave.
- Fig. 2A is a frequency spectrum of the transmission signal in a case in which nonlinear distortion did not occur.
- Fig. 2B is a frequency spectrum of the transmission signal in a case in which nonlinear distortion occurred. As illustrated in Fig. 2B , in a case in which nonlinear distortion occurred, the side-lobes of the spectrum are raised. Accordingly, because power leaking into adjacent channels increases, the communication quality of the adjacent channels is reduced.
- a distortion compensation amplifier using a pre-distortion technique exists.
- a transmission signal to be input to a transmission amplifier is corrected in advance, for nonlinear distortion which is to occur in the transmission amplifier, using distortion compensation data having characteristics that are inverse to the characteristics of the nonlinear distortion.
- the characteristics of the nonlinear distortion change because of changes that occurred in the transmission amplifier over time. For this reason, updating of the distortion compensation data is necessary.
- one portion of the transmission signal that is an output signal of the transmission amplifier and that has been corrected using the distortion compensation data is fed back as a feedback signal.
- the feedback signal is compared with the transmission signal prior to being corrected using the distortion compensation data to obtain a comparison result.
- the distortion compensation data stored in a distortion compensation table are updated in accordance with the comparison result.
- a reflected signal (a return signal) occurs because the transmission signal is reflected by an antenna, and the reflected signal leaks into the feedback signal. Accordingly, there is a problem that the distortion compensation data stored in the distortion compensation table are incorrectly updated using the feedback signal.
- Fig. 3 is a diagram illustrating a wireless apparatus used on the TDD system.
- the wireless apparatus includes a distortion compensation amplifier 1, a distortion compensation table section 2, a splitter 3, a switching section 4, an antenna 5, a feedback processing section 6, a reception processing section 7, and a combining section 8.
- Arrows 101 to 104 illustrated in Fig. 3 indicate a transmission signal that is amplified by the distortion compensation amplifier 1.
- Arrows 105 to 108 indicate a return signal that occurs because the transmission signal 104 is reflected by the antenna 5.
- Arrows 111 and 112 indicate a reception signal that is received by the antenna 5. The return signal is indicated using the dotted line.
- the following transmission processing is performed in the transmission time period in the TDD system.
- the transmission signal is input to the distortion compensation amplifier 1.
- the distortion compensation amplifier 1 corrects the transmission signal using a distortion compensation data that is notified from the distortion compensation table section 2, and amplifies the corrected transmission signal so that the transmission signal will have a predetermined level.
- the distortion compensation table section 2 stores distortion compensation data corresponding to levels of the transmission signal, and notifies the distortion compensation amplifier 1 of the distortion compensation data corresponding to a level of the transmission signal that has been input.
- the splitter 3 splits the transmission signal 101, which has been amplified by the distortion compensation amplifier 1, into the transmission signal 103 to be transferred in a transmission direction toward the antenna 5 and the transmission signal 102 (hereinafter, described as a "feedback signal” in some cases) to be transferred to a distortion compensation loop.
- the transmission signal 103 is obtained by splitting with the insertion loss of the splitter 3, and the transmission signal 102 is obtained by splitting with a loss corresponding to the degree of coupling of the splitter 3.
- the switching section 4 transfers, in the transmission direction, the transmission signal 103 that has been obtained by splitting performed by the splitter 3.
- the antenna 5 emits, as a wireless signal, the transmission signal 104 that has been transferred by the switching section 4.
- the following reception processing is performed in the reception time period in the TDD system.
- the antenna 5 receives a reception wave, and transfers the reception signal 111.
- the switching section 4 transfers the reception signal 111 to the reception processing section 7 in a reception direction.
- the reception processing section 7 performs reception processing on the reception signal 112 that has been transferred by the switching section 4, and outputs the reception signal 112 as a reception signal.
- the splitter 3 be a directional coupler which transfers most of the transmission signal from the distortion compensation amplifier 1 to the switching section 4 in the transmission direction, and which transfers one portion of the transmission signal as the feedback signal to the feedback processing section 6.
- the switching section 4 be a circulator which transfers the transmission signal from the splitter 3 to the antenna 5 in the transmission direction, and which transfers the reception signal from the antenna 5 to the reception processing section 7 in the reception direction.
- one portion of the transmission signal 104 is reflected by the antenna 5, so that the return signal 105 occurs.
- the reflection is caused by the mismatch between the characteristic impedance of a feeding line in which the transmission signal 104 is transmitted (a line connecting the switching section 4 and the antenna 5 illustrated in Fig. 3 ) and the characteristic impedance of the antenna 5.
- Most of the return signal 105 is transferred as the return signal 107 to the reception processing section 7 in the reception direction.
- one portion of the return signal 105 leaks into a transmission path, along which the transmission signal is transferred, of the switching section 4.
- the one portion of the return signal 105 i.e., the return signal 106, leaks into the splitter 3.
- the combining section 8 adjusts the delay of either of the feedback signal and the return signal which has been subjected to reception processing by the reception processing section 7 so that the timing of the feedback signal and the timing of the return signal will coincide with each other.
- the combining section 8 adjusts the phase and level of the return signal so that the phase and level of the feedback signal and the phase and level of the return signal will coincide with each other. For example, adjustment of the phase of the return signal is performed by a phase shifter, and adjustment of the level of the return signal is performed by an attenuator.
- the combining section 8 combines the feedback signal with the return signal, the feedback signal and the reception signal having been subjected to timing, phase, and level adjustment, thereby generating the feedback signal from which the return signal is removed.
- the timing adjustment performed on the feedback signal or the reception signal may be performed by assuming the transmission/reception timings in the TDD frame described with reference to Fig. 1 to be a reference point.
- a phase shift amount for phase adjustment using the phase shifter and an attenuation for level adjustment using the attenuator are set in advance in consideration of phase conditions and level conditions based on design conditions including conditions for placing the antenna.
- the phase adjustment and the level adjustment may be performed using the phase shift amount and the attenuation, respectively.
- the distortion compensation table section 2 compares, with the transmission signal that has been input, the feedback signal that has been generated by the combining section 8 to obtain a comparison result, and updates the distortion compensation data in accordance with the comparison result.
- Fig. 4 is a flowchart of a distortion compensation flow for explaining a distortion compensation method for the wireless apparatus used on the TDD system.
- step S12 Regarding the feedback signal and the return signal which have been subjected to timing adjustment in step S11 so that the timing of the feedback signal and the timing of the return signal have coincided with each other, the level and phase of the return signal processed by the reception processing section 7 is adjusted so that the level and phase of the return signal processed by the reception processing section 7 will coincide with the level and phase of the return signal which has leaked into the feedback signal.
- step S13 The feedback signal is combined with the reception signal that has been adjusted in step S12, thereby the return signal that has leaked into the feedback signal is removed.
- step S14 The feedback signal that has been combined in step S13 is compared with the transmission signal that has been input to obtain a comparison result.
- the distortion compensation data stored in the distortion compensation table are calculated and updated based on the comparison result.
- reception processing is performed on the return signal in the transmission time period, whereby the return signal that is a signal reflected by the antenna is identified.
- the identified return signal is combined with the feedback signal in the distortion compensation loop. Accordingly, the return signal that has leaked into the feedback signal is removed, and the distortion compensation data is prevented from being incorrectly updated using the return signal that has leaked into the distortion compensation loop.
- Fig. 5 is a diagram for explaining a wireless apparatus used on the TDD system.
- the wireless apparatus includes a distortion compensation amplifier 1, a feedback controller 20, a splitter 3, a switching section 4, a feedback processing section 6, a reception processing section 7, and a combining section 8.
- the combining section 8 corresponds to the combining section 8 illustrated in Fig. 3 , and includes a delay adjustment part 81, a vector adjustment part 82, and a signal combining part 83.
- the arrows 101 to 108, 111, and 112 illustrated in Fig. 5 are the same as those illustrated in Fig. 3 .
- the following transmission processing is performed in the transmission time period in the TDD system.
- a transmission signal is input to the distortion compensation amplifier 1.
- the distortion compensation amplifier 1 corrects the transmission signal using a distortion compensation data that is notified from the feedback control section 20, i.e., using a distortion compensation data that is read by the feedback control section 20 from a distortion compensation table in correspondence with a level of the transmission signal. Then, the distortion compensation amplifier 1 converts the corrected transmission signal into an analog signal, and performs orthogonal modulation using a carrier wave and using a carrier wave having a phase that is shifted by 90 degrees from the phase of the above-mentioned carrier wave, thereby obtaining an orthogonal modulation signal.
- the distortion compensation amplifier 1 converts the frequency of the orthogonal modulation signal into a transmission frequency, and amplifies the orthogonal modulation signal so that the orthogonal modulation signal will have a predetermined level, thereby generating the transmission signal 101.
- the splitter 3 splits the transmission signal 101, which has been generated by the distortion compensation amplifier 1, into the transmission signal 103 to be transferred in a transmission direction toward an antenna and the feedback signal 102 to be transferred to a distortion compensation loop.
- the transmission signal 103 is obtained by splitting with the insertion loss of the splitter 3, and the feedback signal 102 is obtained by splitting with a loss corresponding to the degree of coupling of the splitter 3.
- the switching section 4 transfers, in the transmission direction, the transmission signal 103 that has been obtained by splitting performed by the splitter 3.
- the antenna 5 emits, as a wireless signal, the transmission signal 104 that has been transferred by the switching section 4.
- the feedback processing section 6 performs reception processing on the feedback signal 102 into which the return signal 108 has leaked.
- the feedback processing section 6 performs frequency conversion (down-conversion) on the feedback signal 102 by mixing with the feedback signal 102 using an oscillation signal that is generated by a local oscillator (not illustrated). Then, the feedback processing section 6 performs orthogonal demodulation processing and digital conversion processing.
- the reception processing section 7 Attenuates the return signal 107 so that the return signal 107 will have a predetermined level, and performs reception processing. In the reception time period, the reception processing section 7 performs reception processing without attenuating the reception signal 112. In other words, the reception processing section 7 amplifies the attenuated return signal 107 or the reception signal 112, and performs down-conversion, orthogonal demodulation processing, and digital conversion processing as in the case of the feedback processing section 6.
- the delay adjustment part 81 receives the feedback signal, into which the return signal has leaked and which has been subjected to reception processing by the feedback processing section 6, and the return signal, which has been subjected to reception processing by the reception processing section 7.
- the delay adjustment part 81 performs timing adjustment so that the timing of the feedback signal and the timing of the return signal will coincide with each other. For example, which timing is earlier, the delay of the signal whose timing is the earlier timing is adjusted so that the timing of the feedback signal and the timing of the return signal will coincide with each other.
- the vector adjustment part 82 adjusts the phase and level of the return signal 107 which has been subjected to reception processing by the reception processing section 7 so that the phase and level of the return signal 107 will coincide with those of the return signal 108 which has leaked into the feedback signal.
- adjustment of the phase of the return signal is performed by a phase shifter, and adjustment of the level of the return signal is performed by an attenuator.
- a phase shift amount and a level amount are set in advance. The phase adjustment and the level adjustment may be performed so that the phase shift amount and the level amount will be added into initialization values (default values) of a phase shift adjustment amount and a level adjustment amount, respectively.
- a phase shift amount for phase adjustment using the phase shifter and an attenuation for level adjustment using the attenuator are set in advance in consideration of phase conditions and level conditions based on design conditions including conditions for placing the antenna.
- the signal combining part 83 combines, with the feedback signal, the return signal that has been adjusted by the vector adjustment part 82.
- the timing, phase, and level of the return signal that has leaked into the feedback signal and the timing, phase, and level of the return signal that has been subjected to reception processing are adjusted by the delay adjustment part 81 and the vector adjustment part 82.
- the signal combining part 83 removes the return signal that has leaked into the feedback signal.
- the feedback control section 20 compares, with the level of the transmission signal that has been input, the level of the feedback signal that has been combined by the signal combining part 83 to obtain a comparison result.
- the feedback control section 20 feeds back the comparison result to the delay adjustment part 81 for timing adjustment and to the vector adjustment part 82 for vector adjustment.
- signal lines with the dotted line indicate adjustment feedback signals that are supplied from the feedback control section 20 to the delay adjustment part 81 and the vector adjustment part 82.
- the feedback control section 20 calculates and updates, in accordance with the comparison result, the distortion compensation data that are stored in the distortion compensation table.
- processing performed by the feedback control section 20 including processing performed by the delay adjustment part 81, the vector adjustment part 82, and the signal combining part 83 may be performed by a processor such as a digital signal processor (DSP).
- DSP digital signal processor
- Fig. 6 is a flowchart of a distortion compensation flow for explaining a distortion compensation method for the wireless apparatus used on the TDD system.
- the delay adjustment part 81 illustrated in Fig. 5 adjusts the timing of the feedback signal processed by the feedback processing section 6 and the timing of the return signal processed by the reception processing section 7. For example, which timing is earlier, the delay of the signal whose timing is the earlier timing is adjusted so that the timing of the feedback signal and the timing of the return signal will coincide with each other.
- the vector adjustment part 82 adjusts the level and phase of the return signal subjected to reception processing so that the level and phase of the return signal subjected to reception processing will coincide with those of the return signal which has leaked into the feedback signal. For example, a phase shift amount and a level amount are set in advance. The phase adjustment and the level adjustment are performed so that the phase shift amount and the level amount will be added into initialization values (default values) of a phase shift adjustment amount and a level adjustment amount, respectively.
- the signal combining part 83 combines the feedback signal with the return signal that has been adjusted in step S22, thereby the return signal that has leaked into the feedback signal is removed.
- the feedback control section 20 compares, with the transmission signal that has been input, the feedback signal that has been combined in step S23 to obtain a comparison result.
- the feedback control section 20 determines whether or not the comparison result (comparison characteristics) is favorable. For example, the feedback control section 20 determines whether or not the comparison result satisfies with predetermined comparison characteristics.
- the flow returns to step S22.
- step S22 level adjustment and phase adjustment (vector adjustment) are performed, and whether or not the comparison characteristics are favorable is determined.
- step S21 timing adjustment is performed.
- the flow proceeds to step S25.
- the feedback control section 20 calculates and updates, in accordance with the comparison result obtained in step S24, the distortion compensation data that are stored in the distortion compensation table.
- the predetermined characteristics in step S24 are characteristics having a certain range. However, the following case is supposed: in step S24, the flow returns to step S21 and timing adjustment is performed again; the flow returns to step S22 and vector adjustment is performed; and, even with timing adjustment and vector adjustment, satisfactory comparison characteristics are not obtained. In an abnormal case such as the above case, the feedback control section 20 generates an alarm, and finishes the flow without performing updating of the distortion compensation table in step S25.
- control in the distortion compensation flow is performed in the transmission time period in the TDD system.
- Control including control of feeding back the comparison result to the delay adjustment part 81 and the vector adjustment part 82, control of combing the feedback signal with the reception signal using the signal combining part 83, determination of the comparison result, and control performed for the abnormal case that is described above as one example may be performed by a processor such as a DSP.
- Fig. 7 is a diagram for explaining a directional coupler. It is preferable that a directional coupler 31 be used as the splitter 3.
- the directional coupler 31 transfers, to a terminal 2, a signal that has been input to a terminal 1.
- the directional coupler 31 splits the signal that has been input to the terminal 1, and transfers, to a terminal 4, one portion of the signal that has been input to the terminal 1.
- the directional coupler 31 is applied as the splitter 3 illustrated in Fig. 3 or Fig. 5 , the transmission signal 101 transferred from the distortion compensation amplifier 1 is input to the terminal 1.
- the transmission signal 103 to be transferred to the switching section 4 is output from the terminal 2.
- the feedback signal 102 is output from the terminal 4.
- a directional coupler is managed, typically, using characteristics including an insertion loss L defined for a path from a terminal 1 to a terminal 2, a degree of coupling C defined for a path from the terminal 1 to a terminal 4, an isolation I defined for a path from the terminal 1 to a terminal 3, and a directivity D defined for a path from the terminal 4 to the terminal 3.
- Fig. 8 is a diagram for explaining a circulator. It is preferable that a circulator 41 be used as the switching section 4.
- the circulator 41 transfers each signal in one direction so that it transfers, to a terminal 2, a signal that has been input to a terminal 1, and it transfers, to a terminal 3, a signal that has been input to the terminal 2.
- the transmission signal 103 transferred from the splitter 3 is input to the terminal 1.
- the transmission signal 104 to be transferred to the antenna 5 is output from the terminal 2.
- the reception signal 111 received by the antenna 5 or the return signal 105 reflected by the antenna 5 is input to the terminal 2.
- the reception signal 111 that has been input to the terminal 2 is output from the terminal 3 as the reception signal 112 to be transferred to the reception processing section 7.
- the return signal 105 that has been input to the terminal 2 is output from the terminal 3 as the return signal 107 to be transferred to the reception processing section 7.
- a circulator is managed, typically, using characteristics including an insertion loss and a backward insertion loss.
- Fig. 9 is a diagram for explaining a distortion compensation amplifier and a feedback controller.
- the distortion compensation amplifier 1 illustrated in Fig. 3 or Fig. 5 and the feedback controller 20 illustrated in Fig. 5 will be described in detail with reference to Fig. 9 .
- the transmission signal constituted by I and Q signals that are to be subjected to orthogonal modulation is input to an input detection part 21.
- the input detection part 21 detects a level of the transmission signal that has been input.
- the transmission signal is a signal that is to be transmitted in the transmission time period described with reference to Fig. 1 .
- a distortion compensation table 22 is notified of the level of the transmission signal that has been detected by the input detection part 21.
- a distortion compensation data corresponding to the level of the transmission signal is read from the distortion compensation table 22 (the distortion compensation table section 2 illustrated in Fig. 3 ), and supplied to a pre-distorter 11.
- the pre-distorter 11 corrects, using the distortion compensation data corresponding to the level of the transmission signal, the transmission signal that has been input.
- a digital-to-analog (D/A) converter 12 converts, into an analog signal, the transmission signal that has been corrected by the pre-distorter 11.
- An orthogonal modulator 13 performs orthogonal modulation, using a reference carrier wave and using a carrier wave having a phase that is shifted by 90 degrees from the phase of the reference carrier wave, on the transmission signal (constituted by the I and Q signals) that is an analog signal obtained by conversion performed by the D/A converter 12.
- a frequency converter 14 performs frequency conversion (up-conversion) to convert, into a signal in a wireless frequency band, the transmission signal that has been modulated by the orthogonal modulator 13.
- An amplifier 15 amplifies the transmission signal which has been up-converted by the frequency converter 14 so that the transmission signal will have a predetermined power level.
- the input detection part 21 detects the level of the transmission signal that has been input, and notifies the distortion compensation table 22 and a level comparing part 23 of an information item concerning the detected level.
- the distortion compensation table 22 stores distortion compensation data corresponding to levels of the transmission signal.
- the distortion compensation table 22 supplies, to the distortion compensation amplifier 1, the distortion compensation data corresponding to the level of the transmission signal notified from the input detection part 21. Furthermore, the distortion compensation table 22 calculates, in accordance with a comparison information item notified from the level comparing part 23, the distortion compensation data for nonlinear distortion characteristics that changed because of changes which occurred in a transmission amplifier (the amplifier 15) over time.
- the distortion compensation table 22 updates the distortion compensation data.
- the level comparing part 23 performs comparison processing, i.e., compares, with the level of the feedback signal that has been subjected to combining processing by the signal combining part 83 illustrated in Fig. 5 , the level of the transmission signal that has been detected by the input detection part 21 to obtain a comparison result.
- the comparison processing is performed in the transmission time period described with reference to Fig. 1 .
- the comparison result is fed back to the delay adjustment part 81 and the vector adjustment part 82 that are illustrated in Fig. 5 .
- the distortion compensation table 22 is notified of an information item with which the comparison result will be made favorable, e.g., a comparison information item with which the difference between the level of the transmission signal and the level of the feedback signal will be reduced.
- Fig. 10 is a diagram for explaining a feedback processing section.
- the feedback processing section 6 illustrated in Fig. 3 or Fig. 5 will be described in detail with reference to Fig. 10 .
- the transmission signal 102 (hereinafter, described as a "feedback signal” in some cases) that is one portion of the transmission signal obtained by splitting performed by the splitter 3 illustrated in Fig. 3 or Fig. 5 is input to a frequency converter 61.
- the frequency converter 61 performs frequency conversion (down-conversion) to convert the feedback signal in the wireless frequency band into a signal in a predetermined frequency band.
- An orthogonal demodulator 62 performs orthogonal demodulation, using a reference carrier wave and using a carrier wave having a phase that is shifted by 90 degrees from the phase of the reference carrier wave, on the feedback signal that has been down-converted by the frequency converter 61.
- An A/D converter 63 converts, into a digital signal, the feedback signal (constituted by I and Q signals) that has been demodulated by the orthogonal demodulator 62.
- the feedback signal that is a digital signal obtained by conversion is transferred to the delay adjustment part 81 illustrated in Fig. 5 (the combining section 8 illustrated in Fig. 3 ).
- Fig. 11 is a diagram for explaining a reception processing section.
- the reception processing section 7 illustrated in Fig. 3 or Fig. 5 will be described in detail with reference to Fig. 11 .
- the switching section 4 described with reference to Fig. 3 or Fig. 5 transfers, to a variable attenuator 71, the signal (the return signal) that has occurred because the transmission signal has been reflected by the antenna 5.
- the switching section 4 transfers, to the variable attenuator 71, the reception signal that has been received by the antenna 5.
- transmission power for the transmission signal 104 illustrated in Fig. 3 or Fig. 5 is 10 W (40 dBm). It is supposed that the lowest level of a signal that the wireless apparatus receives is -90 dBm. It is considered that the worst (highest) level of a signal (the return signal) which occurs because the transmission signal is reflected by the antenna 5 is 30 dBm.
- the level of a signal that the switching section 4 transfers to the variable attenuator 71 is 30 dBm (the level of the return signal) in the transmission time period, and is -90 dBm (the level of the reception signal) in the reception time period.
- the return signal having the worst level of 30 dBm is input to the variable attenuator 71 illustrated in Fig. 11 .
- the reception time period when the level of the reception signal is the lowest, the reception signal having the lowest level of -90 dBm is input to the variable attenuator 71.
- LNA low noise amplifier
- variable attenuator 71 attenuates the return signal in the transmission time period in accordance with a TDD switching signal with which the transmission time period and the reception time period are distinguished from each other.
- the amplifier 72 provided at the next stage and the parts subsequent thereto perform the same reception processing on both the reception signal and the return signal. Accordingly, the attenuation of the variable attenuator 71 is set to a predetermined attenuation with which the return signal is attenuated so that the level of the return signal will be as low as the level of the reception signal.
- the amplifier 72 amplifies the return signal so that the return signal will have a predetermined level.
- the amplifier 72 amplifies the reception signal so that the reception signal will have the predetermined level.
- a frequency converter 73 down-converts the amplified return signal or reception signal into a signal in a predetermined frequency band.
- An orthogonal demodulator 74 performs orthogonal demodulation, using a reference carrier wave and using a carrier wave having a phase that is shifted by 90 degrees from the phase of the reference carrier wave, on the return signal or reception signal that has been subjected to frequency conversion by the frequency converter 73.
- An A/D converter 75 converts, into a digital signal, the return signal or reception signal (constituted by I and Q signals) that has been demodulated by the orthogonal demodulator 74.
- the return signal that is a digital signal obtained by conversion is transferred to the delay adjustment part 81 illustrated in Fig. 5 (the combining section 8 in Fig. 3 ).
- the reception signal that is a digital signal obtained by conversion is transferred to a block (not illustrated) that is provided at the next stage and that is to process the reception signal.
- reception processing is performed on the return signal in the transmission time period, whereby the return signal that is a signal reflected by the antenna is identified.
- the identified return signal is combined with the feedback signal in the distortion compensation loop.
- the comparison characteristics obtained by comparing the combined feedback signal with the transmission signal that has been input are fed back to the delay adjustment part and the vector adjustment part, whereby timing adjustment and vector adjustment are performed until favorable comparison characteristics are obtained. Accordingly, the return signal that has leaked into the feedback signal is removed, and the distortion compensation data is prevented from being incorrectly updated using the return signal that has leaked into the distortion compensation loop.
- the invention also provides a computer program or a computer program product for carrying out any of the methods described herein, and a computer readable medium having stored thereon a program for carrying out any of the methods described herein.
- a computer program embodying the invention may be stored on a computer-readable medium, or it could, for example, be in the form of a signal such as a downloadable data signal provided from an Internet website, or it could be in any other form.
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- Amplifiers (AREA)
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Abstract
Description
- The embodiments discussed herein are related to a wireless apparatus and a distortion compensation method used on a time division duplex system.
- For wireless communication apparatuses using a multi-phase shift keying modulation system for a high efficiency transmission, significant design conditions for reducing power leakage to adjacent channels by reducing nonlinear distortion of a power amplifier in a transmission unit (hereinafter, described as a "transmission amplifier" in some cases) are provided. For example, in a case in which a channel uses a frequency at a boundary of a frequency band assigned to a carrier, noise occurs to adjacent channels for other carriers because of power leakage from the channel in a wireless communication.
- Distortion compensation amplifiers that compensate for nonlinear distortion employ a pre-distortion technique in some cases. In the pre-distortion technique, a transmission signal is corrected in advance using data having characteristics inverse to characteristics of nonlinear distortion (hereinafter, described as "distortion compensation data" in some cases). The corrected signal is used as a signal to be input to a transmission amplifier. Furthermore, in the pre-distortion technique, in order to update the distortion compensation data for changes that occurred in the transmission amplifier over time, one portion of the transmission signal amplified by the transmission amplifier is fed back. The transmission signal is compared with the transmission signal prior to being corrected using the distortion compensation data, and the distortion compensation data are updated. Hereinafter, a loop system including the transmission amplifier and a feedback system that are used to update the distortion compensation data is described as a "distortion compensation loop" in some cases.
- Accordingly, a signal that is fed back in the distortion compensation loop (hereinafter, described as a "feedback signal" in some cases) is required that the signal has characteristics of an output signal of the transmission amplifier.
- However, the transmission signal is reflected by an antenna because of fluctuation in load imposed on the antenna that is caused by deterioration of conditions for placing the antenna or the like. Then, in some cases, the reflected transmission signal (hereinafter, described as a "return signal" in some cases) leaks into the distortion compensation loop. Accordingly, the feedback signal is not considered as a signal that is obtained in consideration of the output signal of the transmission amplifier. As a technique for solving the above-mentioned problem, a technique is disclosed, in which a vector adjustment circuit capable of performing phase adjustment or amplitude adjustment is provided, and in which cancellation of a return signal that has leaked into a feedback signal is performed (see International Publication Pamphlet No.
WO2006/059372 ). - Accordingly, it is desirable to provide a wireless apparatus that is a wireless apparatus using the time division duplex system (TDD system), and that combines, with a return signal which is transmitted in a reception unit using the TDD system, a feedback signal into which a return signal has leaked.
- A wireless apparatus in which a distortion compensation loop is formed so as to compensate nonlinear distortion of a transmission amplifier, being used on a time division duplex system on which a wireless signal is transmitted in a transmission time period with same frequency as being received, the wireless apparatus used on the time division duplex system including a combining section to combine a feedback signal into which a return signal generated by reflection of a transmission signal at a antenna leaks and the return signal processed by a reception unit to process a reception signal from the antenna in the transmission time period so as to cancel the return signal leaked into the feedback signal.
- The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims.
- It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed.
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Fig. 1 is a diagram for explaining a time division duplex system (TDD system); -
Figs. 2A to 2B are diagrams illustrating frequency spectra of a transmission signal for explaining influence of nonlinear distortion; -
Fig. 3 is a diagram for explaining a wireless apparatus used on the TDD system according to a first embodiment; -
Fig. 4 is a flowchart of a distortion compensation flow for explaining a distortion compensation method for the wireless apparatus used on the TDD system according to the first embodiment; -
Fig. 5 is a diagram for explaining a wireless apparatus used on the TDD system according to a second embodiment; -
Fig. 6 is a flowchart of a distortion compensation flow for explaining a distortion compensation method for the wireless apparatus used on the TDD system according to the second embodiment; -
Fig. 7 is a diagram for explaining a directional coupler; -
Fig. 8 is a diagram for explaining a circulator; -
Fig. 9 is a diagram for explaining a distortion compensation amplifier and a feedback controller; -
Fig. 10 is a diagram for explaining a feedback processing section; and -
Fig. 11 is a diagram for explaining a reception processing section. - Hereinafter, embodiments will be described with reference to the drawings. Note that, in the drawings, elements that are the same as or similar to each other are denoted by the same referential numerals.
- In the distortion compensation amplifiers using the pre-distortion technique, it is necessary to prevent the distortion compensation data from being incorrectly updated using the return signal that has leaked into the distortion compensation loop. First, a time division duplex system (TDD system) and nonlinear distortion will be described.
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Fig. 1 is a diagram for explaining a TDD system. For example, a base station (BS) and mobile stations (MS) 1 to 3 exist in the same cell. The base station (BS) and the mobile stations (MS) 1 to 3 alternately perform transmission and reception of signals therebetween at different timings in TDD frames using the same frequency.Fig. 1 illustrates a four-channel multiplexing multicarrier system. Each of the TDD frames is divided into a transmission time period, in which communication in a downward direction from the base station (BS) to a mobile station (MS) is performed, and a reception time period, in which communication in an upward direction from a mobile station (MS) to the base station (BS). Four time slots are assigned to each of the transmission time period and the reception time period. For example, time slots T1 to T4 are assigned to the transmission time period, and time slots R1 to R4 are assigned to the reception time period. The time slots T1 and R1 are control channels, and are used to perform transmission/reception of a control signal between the base station (BS) and each of the mobile stations (MS) in a corresponding one of the TDD frames. In other words, in the control channel of a first TDD frame, the base station (BS) and the mobile station 1 (MS1) perform transmission/reception of a control signal therebetween. In the control channel of a second TDD frame, the base station (BS) and the mobile station 2 (MS2) perform transmission/reception of a control signal therebetween. In the control channel of a third TDD frame, the base station (BS) and the mobile station 3 (MS3) perform transmission/reception of a control signal therebetween. The time slots T2 to T4 and R2 to R4 are communication channels. In the communication channels, the base station (BS) and each of the mobile stations (MS) perform transmission/reception of communication signals therebetween in a corresponding one of the TDD frames. -
Figs. 2A to 2B are diagrams illustrating frequency spectra of a transmission signal for explaining influence of nonlinear distortion, and illustrate a case in which the transmission signal is transmitted as one carrier wave.Fig. 2A is a frequency spectrum of the transmission signal in a case in which nonlinear distortion did not occur.Fig. 2B is a frequency spectrum of the transmission signal in a case in which nonlinear distortion occurred. As illustrated inFig. 2B , in a case in which nonlinear distortion occurred, the side-lobes of the spectrum are raised. Accordingly, because power leaking into adjacent channels increases, the communication quality of the adjacent channels is reduced. - As a distortion compensation amplifier that compensates for the nonlinear distortion, a distortion compensation amplifier using a pre-distortion technique exists. In the pre-distortion technique, a transmission signal to be input to a transmission amplifier is corrected in advance, for nonlinear distortion which is to occur in the transmission amplifier, using distortion compensation data having characteristics that are inverse to the characteristics of the nonlinear distortion. In the distortion compensation amplifier using the pre-distortion technique, the characteristics of the nonlinear distortion change because of changes that occurred in the transmission amplifier over time. For this reason, updating of the distortion compensation data is necessary. In order to update the distortion compensation data, one portion of the transmission signal that is an output signal of the transmission amplifier and that has been corrected using the distortion compensation data is fed back as a feedback signal. The feedback signal is compared with the transmission signal prior to being corrected using the distortion compensation data to obtain a comparison result. The distortion compensation data stored in a distortion compensation table are updated in accordance with the comparison result.
- A reflected signal (a return signal) occurs because the transmission signal is reflected by an antenna, and the reflected signal leaks into the feedback signal. Accordingly, there is a problem that the distortion compensation data stored in the distortion compensation table are incorrectly updated using the feedback signal. Next, a wireless apparatus used on the TDD system for solving the above-mentioned problem will be described.
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Fig. 3 is a diagram illustrating a wireless apparatus used on the TDD system. The wireless apparatus includes adistortion compensation amplifier 1, a distortioncompensation table section 2, asplitter 3, aswitching section 4, anantenna 5, afeedback processing section 6, areception processing section 7, and a combiningsection 8. -
Arrows 101 to 104 illustrated inFig. 3 indicate a transmission signal that is amplified by thedistortion compensation amplifier 1.Arrows 105 to 108 indicate a return signal that occurs because thetransmission signal 104 is reflected by theantenna 5.Arrows antenna 5. The return signal is indicated using the dotted line. - The following transmission processing is performed in the transmission time period in the TDD system. The transmission signal is input to the
distortion compensation amplifier 1. Thedistortion compensation amplifier 1 corrects the transmission signal using a distortion compensation data that is notified from the distortioncompensation table section 2, and amplifies the corrected transmission signal so that the transmission signal will have a predetermined level. The distortioncompensation table section 2 stores distortion compensation data corresponding to levels of the transmission signal, and notifies thedistortion compensation amplifier 1 of the distortion compensation data corresponding to a level of the transmission signal that has been input. Thesplitter 3 splits thetransmission signal 101, which has been amplified by thedistortion compensation amplifier 1, into thetransmission signal 103 to be transferred in a transmission direction toward theantenna 5 and the transmission signal 102 (hereinafter, described as a "feedback signal" in some cases) to be transferred to a distortion compensation loop. Thetransmission signal 103 is obtained by splitting with the insertion loss of thesplitter 3, and thetransmission signal 102 is obtained by splitting with a loss corresponding to the degree of coupling of thesplitter 3. Theswitching section 4 transfers, in the transmission direction, thetransmission signal 103 that has been obtained by splitting performed by thesplitter 3. Theantenna 5 emits, as a wireless signal, thetransmission signal 104 that has been transferred by theswitching section 4. - The following reception processing is performed in the reception time period in the TDD system. The
antenna 5 receives a reception wave, and transfers thereception signal 111. Theswitching section 4 transfers thereception signal 111 to thereception processing section 7 in a reception direction. Thereception processing section 7 performs reception processing on thereception signal 112 that has been transferred by theswitching section 4, and outputs thereception signal 112 as a reception signal. - Accordingly, it is preferable that the
splitter 3 be a directional coupler which transfers most of the transmission signal from thedistortion compensation amplifier 1 to theswitching section 4 in the transmission direction, and which transfers one portion of the transmission signal as the feedback signal to thefeedback processing section 6. It is preferable that theswitching section 4 be a circulator which transfers the transmission signal from thesplitter 3 to theantenna 5 in the transmission direction, and which transfers the reception signal from theantenna 5 to thereception processing section 7 in the reception direction. - Furthermore, in the transmission time period in the TDD system, one portion of the
transmission signal 104 is reflected by theantenna 5, so that thereturn signal 105 occurs. The reflection is caused by the mismatch between the characteristic impedance of a feeding line in which thetransmission signal 104 is transmitted (a line connecting theswitching section 4 and theantenna 5 illustrated inFig. 3 ) and the characteristic impedance of theantenna 5. Most of thereturn signal 105 is transferred as thereturn signal 107 to thereception processing section 7 in the reception direction. However, one portion of thereturn signal 105 leaks into a transmission path, along which the transmission signal is transferred, of theswitching section 4. The one portion of thereturn signal 105, i.e., thereturn signal 106, leaks into thesplitter 3. Thereturn signal 106 that has leaked into thesplitter 3, i.e., thereturn signal 108, leaks into thefeedback signal 102. - In the transmission time period in the TDD system, the
feedback processing section 6 performs reception processing on thefeedback signal 102 into which thereturn signal 108 has leaked. Furthermore, thereception processing section 7 performs reception processing on thereturn signal 107. The combiningsection 8 receives the feedback signal, into which the return signal has leaked and which has been subjected to reception processing by thefeedback processing section 6, and the return signal which has been subjected to reception processing by thereception processing section 7. The combiningsection 8 combines the feedback signal with the return signal supplied from thereception processing section 7 as described below. - The combining
section 8 adjusts the delay of either of the feedback signal and the return signal which has been subjected to reception processing by thereception processing section 7 so that the timing of the feedback signal and the timing of the return signal will coincide with each other. Next, the combiningsection 8 adjusts the phase and level of the return signal so that the phase and level of the feedback signal and the phase and level of the return signal will coincide with each other. For example, adjustment of the phase of the return signal is performed by a phase shifter, and adjustment of the level of the return signal is performed by an attenuator. The combiningsection 8 combines the feedback signal with the return signal, the feedback signal and the reception signal having been subjected to timing, phase, and level adjustment, thereby generating the feedback signal from which the return signal is removed. - Note that, for example, the timing adjustment performed on the feedback signal or the reception signal may be performed by assuming the transmission/reception timings in the TDD frame described with reference to
Fig. 1 to be a reference point. A phase shift amount for phase adjustment using the phase shifter and an attenuation for level adjustment using the attenuator are set in advance in consideration of phase conditions and level conditions based on design conditions including conditions for placing the antenna. The phase adjustment and the level adjustment may be performed using the phase shift amount and the attenuation, respectively. - The distortion
compensation table section 2 compares, with the transmission signal that has been input, the feedback signal that has been generated by the combiningsection 8 to obtain a comparison result, and updates the distortion compensation data in accordance with the comparison result. -
Fig. 4 is a flowchart of a distortion compensation flow for explaining a distortion compensation method for the wireless apparatus used on the TDD system. - S11: Regarding the feedback signal processed by the
feedback processing section 6 and the return signal processed by thereception processing section 7 illustrated inFig. 3 , which timing is earlier, the timing of the feedback signal or the timing of the return signal, and the delay of the signal whose timing is the earlier timing is adjusted so that the timing of the feedback signal and the timing of the return signal will coincide with each other. - S12: Regarding the feedback signal and the return signal which have been subjected to timing adjustment in step S11 so that the timing of the feedback signal and the timing of the return signal have coincided with each other, the level and phase of the return signal processed by the
reception processing section 7 is adjusted so that the level and phase of the return signal processed by thereception processing section 7 will coincide with the level and phase of the return signal which has leaked into the feedback signal. - S13: The feedback signal is combined with the reception signal that has been adjusted in step S12, thereby the return signal that has leaked into the feedback signal is removed.
- S14: The feedback signal that has been combined in step S13 is compared with the transmission signal that has been input to obtain a comparison result. The distortion compensation data stored in the distortion compensation table are calculated and updated based on the comparison result.
- According to the first embodiment, using the reception processing section that processes the reception signal in the reception time period in the TDD system, reception processing is performed on the return signal in the transmission time period, whereby the return signal that is a signal reflected by the antenna is identified. The identified return signal is combined with the feedback signal in the distortion compensation loop. Accordingly, the return signal that has leaked into the feedback signal is removed, and the distortion compensation data is prevented from being incorrectly updated using the return signal that has leaked into the distortion compensation loop.
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Fig. 5 is a diagram for explaining a wireless apparatus used on the TDD system. The wireless apparatus includes adistortion compensation amplifier 1, afeedback controller 20, asplitter 3, aswitching section 4, afeedback processing section 6, areception processing section 7, and a combiningsection 8. The combiningsection 8 corresponds to the combiningsection 8 illustrated inFig. 3 , and includes adelay adjustment part 81, avector adjustment part 82, and asignal combining part 83. Thearrows 101 to 108, 111, and 112 illustrated inFig. 5 are the same as those illustrated inFig. 3 . - The following transmission processing is performed in the transmission time period in the TDD system.
- A transmission signal is input to the
distortion compensation amplifier 1. Thedistortion compensation amplifier 1 corrects the transmission signal using a distortion compensation data that is notified from thefeedback control section 20, i.e., using a distortion compensation data that is read by thefeedback control section 20 from a distortion compensation table in correspondence with a level of the transmission signal. Then, thedistortion compensation amplifier 1 converts the corrected transmission signal into an analog signal, and performs orthogonal modulation using a carrier wave and using a carrier wave having a phase that is shifted by 90 degrees from the phase of the above-mentioned carrier wave, thereby obtaining an orthogonal modulation signal. Thedistortion compensation amplifier 1 converts the frequency of the orthogonal modulation signal into a transmission frequency, and amplifies the orthogonal modulation signal so that the orthogonal modulation signal will have a predetermined level, thereby generating thetransmission signal 101. - The
splitter 3 splits thetransmission signal 101, which has been generated by thedistortion compensation amplifier 1, into thetransmission signal 103 to be transferred in a transmission direction toward an antenna and thefeedback signal 102 to be transferred to a distortion compensation loop. Thetransmission signal 103 is obtained by splitting with the insertion loss of thesplitter 3, and thefeedback signal 102 is obtained by splitting with a loss corresponding to the degree of coupling of thesplitter 3. Theswitching section 4 transfers, in the transmission direction, thetransmission signal 103 that has been obtained by splitting performed by thesplitter 3. Theantenna 5 emits, as a wireless signal, thetransmission signal 104 that has been transferred by theswitching section 4. - In the transmission time period in the TDD system, the
feedback processing section 6 performs reception processing on thefeedback signal 102 into which thereturn signal 108 has leaked. In other words, thefeedback processing section 6 performs frequency conversion (down-conversion) on thefeedback signal 102 by mixing with thefeedback signal 102 using an oscillation signal that is generated by a local oscillator (not illustrated). Then, thefeedback processing section 6 performs orthogonal demodulation processing and digital conversion processing. - In the transmission time period in the TDD system, the
reception processing section 7 attenuates thereturn signal 107 so that thereturn signal 107 will have a predetermined level, and performs reception processing. In the reception time period, thereception processing section 7 performs reception processing without attenuating thereception signal 112. In other words, thereception processing section 7 amplifies theattenuated return signal 107 or thereception signal 112, and performs down-conversion, orthogonal demodulation processing, and digital conversion processing as in the case of thefeedback processing section 6. - In the transmission time period in the TDD system, the
delay adjustment part 81 receives the feedback signal, into which the return signal has leaked and which has been subjected to reception processing by thefeedback processing section 6, and the return signal, which has been subjected to reception processing by thereception processing section 7. Thedelay adjustment part 81 performs timing adjustment so that the timing of the feedback signal and the timing of the return signal will coincide with each other. For example, which timing is earlier, the delay of the signal whose timing is the earlier timing is adjusted so that the timing of the feedback signal and the timing of the return signal will coincide with each other. - In the transmission time period in the TDD system, regarding the feedback signal and the return signal which have been subjected to timing adjustment by the
delay adjustment part 81 so that the timing of the feedback signal and the timing of the reception signal have coincided with each other, thevector adjustment part 82 adjusts the phase and level of thereturn signal 107 which has been subjected to reception processing by thereception processing section 7 so that the phase and level of thereturn signal 107 will coincide with those of thereturn signal 108 which has leaked into the feedback signal. For example, adjustment of the phase of the return signal is performed by a phase shifter, and adjustment of the level of the return signal is performed by an attenuator. A phase shift amount and a level amount are set in advance. The phase adjustment and the level adjustment may be performed so that the phase shift amount and the level amount will be added into initialization values (default values) of a phase shift adjustment amount and a level adjustment amount, respectively. - Note that, as the default values of the phase shift adjustment amount and the level adjustment amount, a phase shift amount for phase adjustment using the phase shifter and an attenuation for level adjustment using the attenuator are set in advance in consideration of phase conditions and level conditions based on design conditions including conditions for placing the antenna.
- The
signal combining part 83 combines, with the feedback signal, the return signal that has been adjusted by thevector adjustment part 82. The timing, phase, and level of the return signal that has leaked into the feedback signal and the timing, phase, and level of the return signal that has been subjected to reception processing are adjusted by thedelay adjustment part 81 and thevector adjustment part 82. Thus, by combining, with the feedback signal, the return signal that has been subjected to reception processing, thesignal combining part 83 removes the return signal that has leaked into the feedback signal. - The
feedback control section 20 compares, with the level of the transmission signal that has been input, the level of the feedback signal that has been combined by thesignal combining part 83 to obtain a comparison result. Thefeedback control section 20 feeds back the comparison result to thedelay adjustment part 81 for timing adjustment and to thevector adjustment part 82 for vector adjustment. (InFig. 5 , signal lines with the dotted line indicate adjustment feedback signals that are supplied from thefeedback control section 20 to thedelay adjustment part 81 and thevector adjustment part 82.) In the transmission time period using the TDD system illustrated inFig. 1 , after adjustment has been performed as described above, thefeedback control section 20 calculates and updates, in accordance with the comparison result, the distortion compensation data that are stored in the distortion compensation table. Note that processing performed by thefeedback control section 20 including processing performed by thedelay adjustment part 81, thevector adjustment part 82, and thesignal combining part 83 may be performed by a processor such as a digital signal processor (DSP). -
Fig. 6 is a flowchart of a distortion compensation flow for explaining a distortion compensation method for the wireless apparatus used on the TDD system. - S21: The
delay adjustment part 81 illustrated inFig. 5 adjusts the timing of the feedback signal processed by thefeedback processing section 6 and the timing of the return signal processed by thereception processing section 7. For example, which timing is earlier, the delay of the signal whose timing is the earlier timing is adjusted so that the timing of the feedback signal and the timing of the return signal will coincide with each other. - S22: Regarding the feedback signal and the return signal subjected to reception processing whose timings have been favorably adjusted in step S21, the
vector adjustment part 82 adjusts the level and phase of the return signal subjected to reception processing so that the level and phase of the return signal subjected to reception processing will coincide with those of the return signal which has leaked into the feedback signal. For example, a phase shift amount and a level amount are set in advance. The phase adjustment and the level adjustment are performed so that the phase shift amount and the level amount will be added into initialization values (default values) of a phase shift adjustment amount and a level adjustment amount, respectively. - S23: The
signal combining part 83 combines the feedback signal with the return signal that has been adjusted in step S22, thereby the return signal that has leaked into the feedback signal is removed. - S24: The
feedback control section 20 compares, with the transmission signal that has been input, the feedback signal that has been combined in step S23 to obtain a comparison result. Thefeedback control section 20 determines whether or not the comparison result (comparison characteristics) is favorable. For example, thefeedback control section 20 determines whether or not the comparison result satisfies with predetermined comparison characteristics. When favorable comparison characteristics are not obtained, first, the flow returns to step S22. In step S22, level adjustment and phase adjustment (vector adjustment) are performed, and whether or not the comparison characteristics are favorable is determined. When favorable comparison characteristics are not obtained with vector adjustment, the flow returns to step S21. In step S21, timing adjustment is performed. In contrast, when favorable comparison characteristics are obtained, the flow proceeds to step S25. - S25: The
feedback control section 20 calculates and updates, in accordance with the comparison result obtained in step S24, the distortion compensation data that are stored in the distortion compensation table. - Note that, the predetermined characteristics in step S24 are characteristics having a certain range. However, the following case is supposed: in step S24, the flow returns to step S21 and timing adjustment is performed again; the flow returns to step S22 and vector adjustment is performed; and, even with timing adjustment and vector adjustment, satisfactory comparison characteristics are not obtained. In an abnormal case such as the above case, the
feedback control section 20 generates an alarm, and finishes the flow without performing updating of the distortion compensation table in step S25. - The above-described control in the distortion compensation flow is performed in the transmission time period in the TDD system. Control including control of feeding back the comparison result to the
delay adjustment part 81 and thevector adjustment part 82, control of combing the feedback signal with the reception signal using thesignal combining part 83, determination of the comparison result, and control performed for the abnormal case that is described above as one example may be performed by a processor such as a DSP. - Hereinafter, more detailed functional blocks of the wireless apparatus using the TDD system will be described.
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Fig. 7 is a diagram for explaining a directional coupler. It is preferable that adirectional coupler 31 be used as thesplitter 3. Thedirectional coupler 31 transfers, to aterminal 2, a signal that has been input to aterminal 1. Thedirectional coupler 31 splits the signal that has been input to theterminal 1, and transfers, to aterminal 4, one portion of the signal that has been input to theterminal 1. When thedirectional coupler 31 is applied as thesplitter 3 illustrated inFig. 3 orFig. 5 , thetransmission signal 101 transferred from thedistortion compensation amplifier 1 is input to theterminal 1. Thetransmission signal 103 to be transferred to theswitching section 4 is output from theterminal 2. Thefeedback signal 102 is output from theterminal 4. A directional coupler is managed, typically, using characteristics including an insertion loss L defined for a path from aterminal 1 to aterminal 2, a degree of coupling C defined for a path from theterminal 1 to aterminal 4, an isolation I defined for a path from theterminal 1 to aterminal 3, and a directivity D defined for a path from theterminal 4 to theterminal 3. -
Fig. 8 is a diagram for explaining a circulator. It is preferable that acirculator 41 be used as theswitching section 4. Thecirculator 41 transfers each signal in one direction so that it transfers, to aterminal 2, a signal that has been input to aterminal 1, and it transfers, to aterminal 3, a signal that has been input to theterminal 2. When thecirculator 41 is applied as theswitching section 4 illustrated inFig. 3 orFig. 5 , thetransmission signal 103 transferred from thesplitter 3 is input to theterminal 1. Thetransmission signal 104 to be transferred to theantenna 5 is output from theterminal 2. Thereception signal 111 received by theantenna 5 or thereturn signal 105 reflected by theantenna 5 is input to theterminal 2. Thereception signal 111 that has been input to theterminal 2 is output from theterminal 3 as thereception signal 112 to be transferred to thereception processing section 7. Thereturn signal 105 that has been input to theterminal 2 is output from theterminal 3 as thereturn signal 107 to be transferred to thereception processing section 7. A circulator is managed, typically, using characteristics including an insertion loss and a backward insertion loss. -
Fig. 9 is a diagram for explaining a distortion compensation amplifier and a feedback controller. Thedistortion compensation amplifier 1 illustrated inFig. 3 orFig. 5 and thefeedback controller 20 illustrated inFig. 5 will be described in detail with reference toFig. 9 . - For example, the transmission signal constituted by I and Q signals that are to be subjected to orthogonal modulation is input to an
input detection part 21. Theinput detection part 21 detects a level of the transmission signal that has been input. Note that the transmission signal is a signal that is to be transmitted in the transmission time period described with reference toFig. 1 . A distortion compensation table 22 is notified of the level of the transmission signal that has been detected by theinput detection part 21. A distortion compensation data corresponding to the level of the transmission signal is read from the distortion compensation table 22 (the distortioncompensation table section 2 illustrated inFig. 3 ), and supplied to a pre-distorter 11. - The pre-distorter 11 corrects, using the distortion compensation data corresponding to the level of the transmission signal, the transmission signal that has been input.
- A digital-to-analog (D/A)
converter 12 converts, into an analog signal, the transmission signal that has been corrected by the pre-distorter 11. - An
orthogonal modulator 13 performs orthogonal modulation, using a reference carrier wave and using a carrier wave having a phase that is shifted by 90 degrees from the phase of the reference carrier wave, on the transmission signal (constituted by the I and Q signals) that is an analog signal obtained by conversion performed by the D/A converter 12. - A
frequency converter 14 performs frequency conversion (up-conversion) to convert, into a signal in a wireless frequency band, the transmission signal that has been modulated by theorthogonal modulator 13. - An
amplifier 15 amplifies the transmission signal which has been up-converted by thefrequency converter 14 so that the transmission signal will have a predetermined power level. - The
input detection part 21 detects the level of the transmission signal that has been input, and notifies the distortion compensation table 22 and alevel comparing part 23 of an information item concerning the detected level. - The distortion compensation table 22 stores distortion compensation data corresponding to levels of the transmission signal. The distortion compensation table 22 supplies, to the
distortion compensation amplifier 1, the distortion compensation data corresponding to the level of the transmission signal notified from theinput detection part 21. Furthermore, the distortion compensation table 22 calculates, in accordance with a comparison information item notified from thelevel comparing part 23, the distortion compensation data for nonlinear distortion characteristics that changed because of changes which occurred in a transmission amplifier (the amplifier 15) over time. The distortion compensation table 22 updates the distortion compensation data. - The
level comparing part 23 performs comparison processing, i.e., compares, with the level of the feedback signal that has been subjected to combining processing by thesignal combining part 83 illustrated inFig. 5 , the level of the transmission signal that has been detected by theinput detection part 21 to obtain a comparison result. The comparison processing is performed in the transmission time period described with reference toFig. 1 . The comparison result is fed back to thedelay adjustment part 81 and thevector adjustment part 82 that are illustrated inFig. 5 . The distortion compensation table 22 is notified of an information item with which the comparison result will be made favorable, e.g., a comparison information item with which the difference between the level of the transmission signal and the level of the feedback signal will be reduced. -
Fig. 10 is a diagram for explaining a feedback processing section. Thefeedback processing section 6 illustrated inFig. 3 orFig. 5 will be described in detail with reference toFig. 10 . - The transmission signal 102 (hereinafter, described as a "feedback signal" in some cases) that is one portion of the transmission signal obtained by splitting performed by the
splitter 3 illustrated inFig. 3 orFig. 5 is input to afrequency converter 61. - The
frequency converter 61 performs frequency conversion (down-conversion) to convert the feedback signal in the wireless frequency band into a signal in a predetermined frequency band. - An
orthogonal demodulator 62 performs orthogonal demodulation, using a reference carrier wave and using a carrier wave having a phase that is shifted by 90 degrees from the phase of the reference carrier wave, on the feedback signal that has been down-converted by thefrequency converter 61. - An A/
D converter 63 converts, into a digital signal, the feedback signal (constituted by I and Q signals) that has been demodulated by theorthogonal demodulator 62. The feedback signal that is a digital signal obtained by conversion is transferred to thedelay adjustment part 81 illustrated inFig. 5 (the combiningsection 8 illustrated inFig. 3 ). -
Fig. 11 is a diagram for explaining a reception processing section. Thereception processing section 7 illustrated inFig. 3 orFig. 5 will be described in detail with reference toFig. 11 . - In the TDD system described with reference to
Fig. 1 , in the transmission time period, theswitching section 4 described with reference toFig. 3 orFig. 5 transfers, to avariable attenuator 71, the signal (the return signal) that has occurred because the transmission signal has been reflected by theantenna 5. In the reception time period, theswitching section 4 transfers, to thevariable attenuator 71, the reception signal that has been received by theantenna 5. - For example, it is supposed that transmission power for the
transmission signal 104 illustrated inFig. 3 orFig. 5 is 10 W (40 dBm). It is supposed that the lowest level of a signal that the wireless apparatus receives is -90 dBm. It is considered that the worst (highest) level of a signal (the return signal) which occurs because the transmission signal is reflected by theantenna 5 is 30 dBm. - In this case, supposing that the insertion loss of the
switching section 4 is 0 dB (approximately 1 dB in reality), the level of a signal that theswitching section 4 transfers to thevariable attenuator 71 is 30 dBm (the level of the return signal) in the transmission time period, and is -90 dBm (the level of the reception signal) in the reception time period. - Note that, supposing that the backward insertion loss of the
switching section 4 is 20 dB and the backward insertion loss of thesplitter 3 is 60 dB, it is considered that the level of the return signal which is to leak into the feedback signal 102 (supposing that the level of the feedback signal 102 -10 dBm) is -50 dBm. - In the transmission time period, when the level of the return signal is the lowest, the return signal having the worst level of 30 dBm is input to the
variable attenuator 71 illustrated inFig. 11 . In the reception time period, when the level of the reception signal is the lowest, the reception signal having the lowest level of -90 dBm is input to thevariable attenuator 71. An amplifier (a low noise amplifier (LNA)) 72 that is provided at the next stage to thevariable attenuator 71 is designed so that theamplifier 72 processes the reception signal having a low level, e.g., the lowest level of approximately -90 dBm. Accordingly, in order to prevent theamplifier 72 from being damaged from the return signal having a high level in the transmission time period, thevariable attenuator 71 attenuates the return signal in the transmission time period in accordance with a TDD switching signal with which the transmission time period and the reception time period are distinguished from each other. Theamplifier 72 provided at the next stage and the parts subsequent thereto perform the same reception processing on both the reception signal and the return signal. Accordingly, the attenuation of thevariable attenuator 71 is set to a predetermined attenuation with which the return signal is attenuated so that the level of the return signal will be as low as the level of the reception signal. - In the transmission time period, the
amplifier 72 amplifies the return signal so that the return signal will have a predetermined level. In the reception time period, theamplifier 72 amplifies the reception signal so that the reception signal will have the predetermined level. - A
frequency converter 73 down-converts the amplified return signal or reception signal into a signal in a predetermined frequency band. - An
orthogonal demodulator 74 performs orthogonal demodulation, using a reference carrier wave and using a carrier wave having a phase that is shifted by 90 degrees from the phase of the reference carrier wave, on the return signal or reception signal that has been subjected to frequency conversion by thefrequency converter 73. - An A/
D converter 75 converts, into a digital signal, the return signal or reception signal (constituted by I and Q signals) that has been demodulated by theorthogonal demodulator 74. The return signal that is a digital signal obtained by conversion is transferred to thedelay adjustment part 81 illustrated inFig. 5 (the combiningsection 8 inFig. 3 ). Furthermore, the reception signal that is a digital signal obtained by conversion is transferred to a block (not illustrated) that is provided at the next stage and that is to process the reception signal. - According to the second embodiment, using the reception processing section that processes the reception signal in the reception time period in the TDD system, reception processing is performed on the return signal in the transmission time period, whereby the return signal that is a signal reflected by the antenna is identified. The identified return signal is combined with the feedback signal in the distortion compensation loop. The comparison characteristics obtained by comparing the combined feedback signal with the transmission signal that has been input are fed back to the delay adjustment part and the vector adjustment part, whereby timing adjustment and vector adjustment are performed until favorable comparison characteristics are obtained. Accordingly, the return signal that has leaked into the feedback signal is removed, and the distortion compensation data is prevented from being incorrectly updated using the return signal that has leaked into the distortion compensation loop.
- In any of the aspects or embodiments of the invention described above, the various features may be implemented in hardware, or as software modules running on one or more processors. Features of one aspect may be applied to any of the other aspects.
- The invention also provides a computer program or a computer program product for carrying out any of the methods described herein, and a computer readable medium having stored thereon a program for carrying out any of the methods described herein.
- A computer program embodying the invention may be stored on a computer-readable medium, or it could, for example, be in the form of a signal such as a downloadable data signal provided from an Internet website, or it could be in any other form.
- All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present inventions have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.
-
Embodiment 1. A wireless apparatus in which a distortion compensation loop is formed so as to compensate nonlinear distortion of a transmission amplifier, being used on a time division duplex system on which a wireless signal is transmitted in a transmission time period with same frequency as being received, the wireless apparatus used on the time division duplex system comprising:- a distortion compensation amplifier to perform a compensation of a transmission signal by using characteristics inverse to characteristics of nonlinear distortion of the transmission signal amplified by a transmission amplifier and transmit the compensated transmission signal;
- a splitter to split the transmission signal compensated by the distortion compensation amplifier into the transmission signal transferred in a transmission direction toward an antenna and the transmission signal in a direction toward the distortion compensation loop;
- a feedback processing section to perform a reception processing on the transmission signal split by the splitter;
- a reception processing section to perform the reception processing on a signal in a reception direction from the antenna;
- a switching section to transfer the compensated transmission signal split by the splitter to the transmission direction and to transfer the signal in the reception direction from the antenna to the reception processing section;
- a delay adjustment part to adjust timings of a feedback signal and a return signal processed by the reception unit in the transmission time period when the transmission signal is transmitted in the transmission direction;
- a vector adjustment part to adjust phases and levels of the feedback signal and the return signal adjusted by the delay adjustment part in the transmission time period;
- a signal combining part to combine the feedback signal and the return signal adjusted by the vector adjustment part in the transmission time period; and
- a feedback controller to update distortion compensation data stored in a distortion compensation table included in the distortion compensation amplifier, in accordance with characteristics of the signal combined by the signal combining part and the transmission signal input to the distortion compensation amplifier, in the transmission time period.
-
Embodiment 2. The wireless apparatus according toembodiment 1, wherein the delay adjustment part adjusts the timings and the vector adjustment part adjusts the phases and levels so that comparison characteristics between the signal combined by the signal combining part and the transmission signal input to the distortion compensation amplifier improve. -
Embodiment 3. The wireless apparatus according toembodiment -
Embodiment 4. The wireless apparatus according to any preceding embodiment, wherein the switching section is a circulator to transfer the transmission signal in the transmission direction to the antenna and transfer the signal in the reception direction from the antenna to the reception processing section. -
Embodiment 5. The wireless apparatus according to any preceding embodiment, wherein the reception processing section includes a variable attenuator to attenuate variably the signal in the reception direction in the transmission time period. -
Embodiment 6. The wireless apparatus according to any preceding embodiment, wherein:- the feedback controller includes:
- an input detection part to detect a signal level of the input transmission signal; and
- the distortion compensation table in which the distortion compensation data used to compensate the input transmission signal based on the input signal level detected by the input detection part are stored;
- the distortion compensation amplifier includes:
- a pre-distorter to compensate the input transmission signal in accordance with the distortion compensation data read out from the distortion compensation table based on the input signal level;
- a D/A converter to convert the input transmission signal to an analog signal thereof;
- an orthogonal modulator to orthogonally transform the input transmission signal converted by the D/A converter;
- a frequency converter to covert a frequency of the signal orthogonally transformed by the orthogonal modulator; and
- an amplifier to amplify power of the transmission signal with the frequency converted by the frequency converter;
- the feedback processing section includes:
- a frequency converter to convert a frequency of the feedback signal from the splitter;
- an orthogonal demodulator to perform orthogonal demodulation of the feedback signal with the frequency converted by the frequency converter; and
- an A/D converter to convert the feedback signal demodulated by the orthogonal demodulator to a digital signal thereof and transmit the feedback signal converted by the A/D converter to the delay adjustment part; and
- the reception processing section includes:
- a variable attenuator to attenuate variably the signal in the reception direction in the transmission time period;
- an amplifier to amplify the signal from the variable attenuator;
- a frequency converter;
- an orthogonal demodulator; and
- an A/D converter;
- wherein the frequency converter, the orthogonal demodulator and the A/D converter have characteristics equivalent to the feedback processing section processing the signal amplified by the amplifier, respectively.
- the feedback controller includes:
-
Embodiment 7. The wireless apparatus according to any preceding embodiment, wherein the transmission signal in the transmission direction from the switching section are transferred to the antenna through a feeding line having a characteristic impedance matching with the characteristic impedance of the antenna. -
Embodiment 8. A wireless apparatus in which a distortion compensation loop is formed so as to compensate nonlinear distortion of a transmission amplifier, being used on a time division duplex system on which a wireless signal is transmitted in a transmission time period with same frequency as being received, the wireless apparatus used on the time division duplex system comprising:- a combining section to combine a feedback signal into which a return signal generated by reflection of a transmission signal at a antenna leaks and the return signal processed by a reception unit to process a reception signal from the antenna in the transmission time period so as to cancel the return signal leaked into the feedback signal.
- Embodiment 9. The wireless apparatus according to
embodiment 8, wherein the combining section includes:- a delay adjustment part to adjust timings of the feedback signal and the return signal processed by the reception unit;
- a vector adjustment part to adjust phases and levels of the feedback signal and the return signal adjusted by the delay adjustment part; and
- a signal combining part to combine the feedback signal and the return signal adjusted by the vector adjustment part.
-
Embodiment 10. A distortion compensation method of a wireless apparatus in which a distortion compensation loop is formed so as to compensate nonlinear distortion of a transmission amplifier, being used on a time division duplex system on which a wireless signal is transmitted in a transmission time period with same frequency as being received, the distortion compensation method comprising:- combining a feedback signal into which a return signal generated by reflection of a transmission signal at a antenna leaks and the return signal processed by a reception unit to process a reception signal from the antenna in the transmission time period so as to cancel the return signal leaked into the feedback signal.
-
Embodiment 11. The distortion compensation method according toembodiment 10, further comprising:- adjusting timings of the feedback signal and the return signal processed by the reception unit;
- adjusting phases and levels of the feedback signal and the return signal; and
- combining the feedback signal and the return signal.
-
Embodiment 12. The distortion compensation method according toembodiment - updating distortion compensation data stored in a distortion compensation table in accordance with comparison characteristics between the feedback signal combined with the return signal processed by the reception unit and an input transmission signal.
-
Embodiment 13. The distortion compensation method according toembodiment 11, orembodiment 12 when read as dependent onembodiment 11, wherein the timings, phases and levels are adjusted so that comparison characteristics between the feedback signal combined with the return signal processed by the reception unit and an input transmission signal improve.
Claims (8)
- A wireless apparatus in which a distortion compensation loop is formed so as to compensate nonlinear distortion of a transmission amplifier by using distortion compensation data and to update the distortion compensation data, being used on a time division duplex system on which a wireless signal is transmitted in a transmission time period with same frequency as received in a reception time period, the wireless apparatus used on the time division duplex system comprising:a combining section (8) configured to combine a reception processed feedback signal (102) into which a return signal (108) generated by reflection of a transmission signal (104) at a antenna (5) leaks and the return signal reception processed in the transmission time period by a reception processing unit (7), which is also configured to reception process a reception signal (112) from the antenna in the reception time period, so as to remove the return signal leaked into the feedback signal from the feedback signal.
- The wireless apparatus according to claim 1, wherein the combining section includes:a delay adjustment part configured to adjust timings of the feedback signal and the return signal reception processed by the reception processing unit;a vector adjustment part configured to adjust phases and levels of the feedback signal and the return signal adjusted by the delay adjustment part; anda signal combining part configured to combine the feedback signal and the return signal adjusted by the vector adjustment part.
- The wireless apparatus according to claim 1 or 2, further comprising:a distortion compensation table (2) for storing updated distortion compensation data in accordance with comparison characteristics between the feedback signal combined with the return signal.
- A distortion compensation method of a wireless apparatus in which a distortion compensation loop is formed so as to compensate nonlinear distortion of a transmission amplifier by using distortion compensation data and to update the distortion compensation data, the wireless apparatus being used on a time division duplex system on which a wireless signal is transmitted in a transmission time period with same frequency as received in a reception time period, the distortion compensation method comprising:combining a reception processed feedback signal (102) into which a return signal (108) generated by reflection of a transmission signal (104) at a antenna (5) leaks and the return signal reception processed in the transmission time period by a reception processing unit (7), which is also configured to reception process a reception signal (112) from the antenna in the reception time period, so as to remove the return signal leaked into the feedback signal from the feedback signal.
- The distortion compensation method according to claim 4, further comprising:adjusting timings of the feedback signal and the return signal reception processed by the reception processing unit;adjusting phases and levels of the feedback signal and the return signal; andcombining the feedback signal and the return signal.
- The distortion compensation method according to claim 4 or 5, further comprising:updating the distortion compensation data stored in a distortion compensation table (2) in accordance with comparison characteristics between the feedback signal combined with the return signal reception processed by the reception processing unit and an input transmission signal.
- The distortion compensation method according to claim 5, or claim 6 when read as dependent on claim 4, wherein the timings, phases and levels are adjusted so that comparison characteristics between the feedback signal combined with the return signal reception processed by the reception processing unit and an input transmission signal improve.
- A communication system comprising a wireless apparatus according to any of claims 1 to 3 for communicating with a base station.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2009066935A JP5381202B2 (en) | 2009-03-18 | 2009-03-18 | Time-division bidirectional transmission wireless device |
EP10155830.2A EP2230760B1 (en) | 2009-03-18 | 2010-03-08 | Wireless apparatus and distortion compensation method used on time division duplex system |
Related Parent Applications (3)
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EP10155830.2 Division | 2010-03-08 | ||
EP10155830.2A Division EP2230760B1 (en) | 2009-03-18 | 2010-03-08 | Wireless apparatus and distortion compensation method used on time division duplex system |
EP10155830.2A Division-Into EP2230760B1 (en) | 2009-03-18 | 2010-03-08 | Wireless apparatus and distortion compensation method used on time division duplex system |
Publications (2)
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EP2560279A1 true EP2560279A1 (en) | 2013-02-20 |
EP2560279B1 EP2560279B1 (en) | 2014-11-12 |
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EP10155830.2A Not-in-force EP2230760B1 (en) | 2009-03-18 | 2010-03-08 | Wireless apparatus and distortion compensation method used on time division duplex system |
EP12188058.7A Not-in-force EP2560279B1 (en) | 2009-03-18 | 2010-03-08 | Wireless apparatus and distortion compensation method used on time division duplex system |
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EP10155830.2A Not-in-force EP2230760B1 (en) | 2009-03-18 | 2010-03-08 | Wireless apparatus and distortion compensation method used on time division duplex system |
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US (1) | US8483314B2 (en) |
EP (2) | EP2230760B1 (en) |
JP (1) | JP5381202B2 (en) |
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JP5158034B2 (en) * | 2009-08-12 | 2013-03-06 | 富士通株式会社 | Wireless device and signal processing method |
US8365237B2 (en) * | 2010-01-22 | 2013-01-29 | Selim Shlomo Rakib | Method of CATV cable same-frequency time division duplex data transmission |
KR20140019591A (en) * | 2012-08-06 | 2014-02-17 | 삼성전기주식회사 | Ofdm receiver with distortion compensation feature, and signal processing method thereof |
US20150092825A1 (en) * | 2013-09-27 | 2015-04-02 | Qualcomm Incorporated | Self-test using internal feedback for transmit signal quality estimation |
JP6453036B2 (en) * | 2014-10-29 | 2019-01-16 | 株式会社マルサン・ネーム | Pressure sensor and contact pressure measuring device |
JP2017005514A (en) * | 2015-06-10 | 2017-01-05 | 富士通株式会社 | Radio equipment |
US10079702B2 (en) * | 2015-07-06 | 2018-09-18 | Mediatek Singapore Pte. Ltd. | Front-end module and coupling compensation for closed-loop digital pre-distortion system |
US10291267B2 (en) * | 2015-08-10 | 2019-05-14 | Maxlinear, Inc. | Band-limited digital pre-distortion (DPD) expansion estimation and curve adjustment |
JP2017059963A (en) | 2015-09-15 | 2017-03-23 | 富士通株式会社 | Radio equipment and distortion cancellation method |
KR102324384B1 (en) * | 2017-05-30 | 2021-11-10 | 삼성전자 주식회사 | Apparatus and method for improving radiation performance of an antenna using impedance tuning |
KR102464946B1 (en) * | 2018-01-31 | 2022-11-09 | 삼성전자주식회사 | Apparatus and method for determining reflection coefficient for antenna |
JP6833149B2 (en) * | 2019-01-16 | 2021-02-24 | 三菱電機株式会社 | Signal sorting circuit, signal sorting method and distortion compensation circuit |
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WO2006059372A1 (en) | 2004-11-30 | 2006-06-08 | Fujitsu Limited | Signal take-out circuit and distortion compensation amplifier comprising it |
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JP3323715B2 (en) | 1995-11-30 | 2002-09-09 | 富士通株式会社 | Wireless device |
US5903823A (en) | 1995-09-19 | 1999-05-11 | Fujitsu Limited | Radio apparatus with distortion compensating function |
FR2835120B1 (en) * | 2002-01-21 | 2006-10-20 | Evolium Sas | METHOD AND DEVICE FOR PREPARING SIGNALS TO BE COMPARED TO ESTABLISH PRE-DISTORTION ON THE INPUT OF AN AMPLIFIER |
JP2004221862A (en) * | 2003-01-14 | 2004-08-05 | Matsushita Electric Ind Co Ltd | Radio communication apparatus |
CN100576724C (en) * | 2005-05-18 | 2009-12-30 | 株式会社Ntt都科摩 | Power series predistorter and control method thereof |
US7783263B2 (en) * | 2006-12-14 | 2010-08-24 | Texas Instruments Incorporated | Simplified digital predistortion in a time-domain duplexed transceiver |
JP2008236021A (en) * | 2007-03-16 | 2008-10-02 | Fujitsu Ltd | Radio communication equipment |
JP2009111958A (en) * | 2007-11-01 | 2009-05-21 | Hitachi Kokusai Electric Inc | Predistorter |
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2009
- 2009-03-18 JP JP2009066935A patent/JP5381202B2/en not_active Expired - Fee Related
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2010
- 2010-03-08 EP EP10155830.2A patent/EP2230760B1/en not_active Not-in-force
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WO2006059372A1 (en) | 2004-11-30 | 2006-06-08 | Fujitsu Limited | Signal take-out circuit and distortion compensation amplifier comprising it |
EP1819038A1 (en) * | 2004-11-30 | 2007-08-15 | Fujitsu Ltd. | Signal take-out circuit and distortion compensation amplifier comprising it |
Also Published As
Publication number | Publication date |
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EP2560279B1 (en) | 2014-11-12 |
EP2230760A2 (en) | 2010-09-22 |
US8483314B2 (en) | 2013-07-09 |
US20100239047A1 (en) | 2010-09-23 |
EP2230760A3 (en) | 2011-03-09 |
EP2230760B1 (en) | 2015-04-01 |
JP5381202B2 (en) | 2014-01-08 |
JP2010220104A (en) | 2010-09-30 |
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